1. Field of the Invention
The present invention generally relates to floating platforms for the offshore production of oil and gas. More particularly, it relates to tension leg platforms (TLPs).
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
The tendon flex bearing is a structural element that allows for relative rotation between the top of the tendon and the tendon porch, i.e. the TLP hull. The tendon flex bearing is in the direct load path of the primary station keeping forces. A typical TLP full life-cycle operational plan does not call for the replacement of these elements.
Station keeping of a typical TLP is provided by a minimum of six tendons. A TLP is designed for extreme and survival conditions, as well as for conditions wherein one tendon missing (i.e., the TLP is re-ballasted to maintain proper tendon tension) and for a broken tendon condition (i.e., no immediate ballast compensation). Though the TLP is designed for such conditions, remedial actions are generally not developed as part of the design process.
Piles driven into the seafloor are attached to the lower ends of the tendons. The upper end of the tendon connects to the TLP hull. The upper end of the tendon itself comprises tendon body elements and, above such, a length adjustment joint (LAJ). The diameter of the LAJ is generally smaller than the diameter of the tendon body. A section of the LAJ is equipped with concentric grooves which allow slips having corresponding projections to clamp onto the tendon (LAJ). These slips, called “the clamp,” are supported by the flex bearing. The flex bearing allows for differential rotation between the tendon body and TLP. The flex bearing may be supported by a load ring which is supported by load cells used to measure the tendon tension. The load cells may be supported by a second load ring that is rigidly attached to the tendon porch which is connected to TLP hull. Alternatively, some TLPs are configured such that the tendon flex bearing is supported directly on the tendon porch or on a ring on the tendon porch. Most of these devices are circular in cross section and, when installed, have a common longitudinal axis. As such, the LAJ (and tendon) are at the center and protrude vertically through the centers of the clamp, the flex bearing, the centers of both load rings and the geometric center of the load cells. FIG. 1 illustrates a typical layout of a tendon and its associated flex bearing.